The invention relates to new and useful improvements in medical systems. More particularly, the invention relates to medical systems, such as X-ray diagnostic devices, having various adjustable components including a patient table and having a control device for determining the position of the components and preventing collisions between them.
In the case of such medical devices, there is a risk that the adjustable components, which can move with several degrees of freedom, will collide with one another. For instance, in the X-ray diagnostic devices mentioned, the image generation system may carry a C-shaped bracket which can be adjusted along its circumference in a mount and which holds the X-ray source and the radiation receiver at its ends. This bracket or the components mounted thereon may inadvertently collide, for example, with the patient table. This risk is all the greater since the operating personnel are often reoccupied with observing the system's screens or with other operations and can therefore concentrate only peripherally on monitoring the movable components.
Various methods are known for avoiding collisions between the C-bracket of an X-ray device and the table or the patient. One such method, a calculating method, is based on a wire model or volume model of the X-ray system. With the aid of the model, the planes of intersection of objects capable of mutually touching can be calculated in a computer. One disadvantage of this method is that a collision is detected only when parts of the system actually touch. Since, however, the drives need a certain distance in order to come to a standstill, the instant of contact is generally already too late. In order to solve this problem, the model can be enlarged by a specific percentage, so that a virtual instant of contact is determined before the actual collision, and hence timely braking is possible. However, in practice it would be desirable for the speed of movement to be reduced already in the case of an approach or in the case of a detectable risk of collision, in order to enable oscillation-free braking of the system. A further problem in the implementation by means of volume modelling, as taught e.g. by German Patent DE 36 04 955 C2, is the enormous computing effort associated with the complex geometric shapes encountered, for example, in an X-ray system.
A quite different method for avoiding collisions is described in German Patent DE 43 35 301 C1. Instead of detecting the position of the components by means of transmitters on the components or the adjusting motors, as in DE 36 04 955 C2, two cameras and a three-dimensional neural network are provided. These observe the movements of the components and intervene appropriately in the case of a risk of collision. One doubtless advantage of such a monitoring device using a three-dimensional neural network is that collisions with movable objects or persons in the examination room can also be detected. However, an associated disadvantage is that the image recording operation is subject to disturbance both by the personnel moving around within the examining room and also by the surfaces of the objects being observed. Although this disadvantage could certainly be circumvented by fitting the system with further cameras, this would further increase the complexity of the system. Even with two cameras, in order to calculate the image data and to reconstruct the objects in the computer, complicated image processing algorithms and appropriately fast computers are necessary, which makes the system very expensive. Accordingly, for the vast majority of applications, the added complexity and expense of this latter method outweighs the associated advantages.